The invention relates to an inking unit in a printing machine, the inking unit being embodied as vibrator-less continuous-type inking unit and having an ink duct or fountain with an ink duct film inserted between an ink metering system, which is subdivided into ink zones, and an ink duct roller.
In the published German Patent Document DE 199 14 179 A1, an ink duct of this type has been described having an ink duct film which is pressed against an ink duct roller by support struts of metering elements of the ink metering system; consequently, the ink duct film is subjected to high mechanical stress. In order nevertheless to assure a long service life of the ink duct film, the latter ink fountain film is provided with low-wear zones formed as wirelike bodies. Although abrasion of the low-wear zones is less than for zones of high wear, nevertheless, the production costs for such an ink duct film are comparatively high. It would be desirable, instead of this complicated, expensive ink duct film, to be able to use a simpler, less expensive ink duct film formed as a disposable item. Each time residual ink remains in the ink duct, and the ink duct film is replaced by another printing ink to be used for a subsequent printing job, it is convenient to throw the ink duct film away and insert a fresh ink duct film into the ink duct. Considering how often ink changes must be made, however, this is feasible only if inexpensive ink duct films can be used.
Furthermore, the published German Patent Document DE 38 04 204 C2 describes a continuous-type inking unit which has an ink duct roller disposed in an ink duct that is equipped with a zonewise regulatable metering system. An unfavorable aspect of this continuous-type inking unit is that cleaning it is tedious; all the residual ink in the ink duct must be removed therefrom with time-consuming labor, using a spatula and cloths. The continuous-type inking unit is therefore suitable only for a roller-type printing press as shown in the last-mentioned German patent document, wherein the interval between cleanings of the ink duct is quite long, because ink is changed only seldom in roller-type printing presses.
Also representing a further state of the art is a vibrator-type inking unit of a sheet-fed printing machine, which is described in the published German Patent Document DE 32 03 500 C3; this inking unit has an ink duct with an ink duct film and an ink duct blade or knife that is subdivided into tongues with scraper edges, for zonal ink metering. Relative to the jacket surface of the ink duct roller, each of the tongues can be set to an open metering gap corresponding to the ink demand in the respective ink zone, and in ink zones not requiring ink, each tongue can be set to a uniform basic position, i.e., a closed zero position. Each tongue set to the basic position presses the ink duct film against the ink duct roller with an initial tension or pretensioning. The pretensioning is due to the assembly operation, wherein each scraper edge, without the ink duct film being in place, is adjusted to a precise amount relative to the jacket surface of the ink duct roller, this amount being equivalent to approximately 50% of the film thickness. In addition, the ink duct film has a smooth and hard surface. Although wear of the ink duct film caused by abrasion by the ink duct roller in the printing operation can possibly be reduced slightly by suitable adjustment of the uniform basic position and by the development of the film surface, nevertheless, the wear cannot be sufficiently prevented in the manner described. The incident wear is admittedly compensated for somewhat by the elasticity of the ink duct film, but the resultant change in the pretensioning causes metering imprecisions because, as the initial tension or pretension lessens because of the pressure head or dynamic pressure of the ink inside an ink zone that intrinsically is kept closed, ink is nevertheless fed between the ink duct roller and the ink duct film and out of the ink duct.
It is accordingly an object of the invention, therefore, to provide an inking unit of the type described at the introduction hereto, which allows simpler, less expensive ink duct films to be used.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, in a printing machine, an inking unit formed as a vibrator-less continuous-type inking unit, comprising an ink duct with an ink duct film inserted between an ink metering system, which is subdivided into ink zones, and an ink duct roller, the ink duct film within each of the ink zones in a region of a settable metering gap being held out of contact with the ink duct roller during printing.
In accordance with another feature of the invention, the inking unit includes a film roller, the ink duct roller and the film roller together defining a film nip therebetween, the width of which remains constant during printing.
In accordance with a further feature of the invention, the ink duct film rests on a base of the ink duct, and the base covers the ink metering system.
In accordance with an added feature of the invention, a central angle of the ink duct roller, the angle being defined by the film nip and by the metering gap between the ink duct film and the ink duct roller, is of 70xc2x0 to 110xc2x0.
In accordance with an additional feature of the invention, t according to claim 2, wherein a central angle of the film roller, the angle being defined by the film nip and by a printing nip between the film roller and an ink roller resting thereon, is of 70xc2x0 to 110xc2x0.
In accordance with yet another feature of the invention, the ink metering system is supported on a bearing bushing of the ink duct roller via an adjusting device.
In accordance with yet a further feature of the invention, the adjusting device rests on a part of the bearing bushing protruding from a frame.
In accordance with yet an added feature of the invention, the adjusting device comprises a threaded pin and a lock nut.
In accordance with yet an additional feature of the invention, respective widths of the ink zones are determined by metering elements of the ink metering system.
In accordance with another aspect of the invention, there is provided a printing machine having an inking unit formed as a vibrator-less continuous-type inking unit, comprising an ink duct with an ink duct film inserted between an ink metering system, which is subdivided into ink zones, and an ink duct roller, the ink duct film within each of the ink zones in a region of a settable metering gap being held out of contact with the ink duct roller during printing.
In accordance with a concomitant aspect of the invention, there is provided a sheet-fed printing machine having an inking unit formed as a vibrator-less continuous-type inking unit, comprising an ink duct with an ink duct film inserted between an ink metering system, which is subdivided into ink zones, and an ink duct roller, the ink duct film within each of the ink zones in a region of a settable metering gap being held out of contact with the ink duct roller during printing.
The inking unit according to the invention, in a printing machine, requires that, during printing, the ink duct film inside of each of the ink zones in the region of a settable metering gap be kept out of contact with the ink duct roller.
A decisive advantage of the inking unit of the invention is that without sacrifices in terms of the metering stability, it allows the use of a simple, inexpensive ink duct film, which is no longer exposed at all to what in the prior art, namely, the published German Patent Document DE 199 14 179 A1, is merely reduced abrasion wear. The residual ink present in the ink duct after a printing job can to a great extent be removed from the ink duct along with the ink duct film. Thereafter, only very quickly performed fine cleaning of the ink duct and the insertion of a clean, new ink duct film into the ink duct are required before the ink to be used for the next printing job is introduced into the ink duct.
Another advantage of the inking unit of the invention is the excellent suitability thereof for use in a sheet-fed printing press. Typical printing jobs for sheet-fed printing presses generally involve a low number of copies and correspondingly a short execution time. Furthermore, these printing jobs often require a change of ink from one printing job to another, for example, because different special or customer-specific inks must be used for each printing job. Consequently, the ink duct of the sheet-fed printing press must be cleaned quite often, and these cleaning operations can be performed without major effort and quickly by the ink duct film of the inking unit according to the invention when it is used in a sheet-fed printing machine.
Yet another advantage of the inking unit of the invention is the very high metering stability and metering precision thereof. Embodying the inking unit as a vibrator-less continuous-type inking unit makes it possible to keep the ink duct film, during printing, in the region located between an ink duct roller and an ink metering system, without any contact at all with the ink duct roller associated with the ink duct, over all the ink zones of the inking unit. During the printing operation, no single ink zone of an ink metering system associated with the ink duct thus has to be closed completely, and so that even inside every ink zone that does not require ink, over the full width of the respective ink zone, only a tiny, pressure-free gap is present between the ink duct film and the ink duct roller. Although, in the ink zone that does not require ink, the ink from the ink duct roller is fed out of the ink duct through the tiny gap, nevertheless a film roller associated with the ink duct roller picks up the ink from the ink duct roller only in ink zones that do require ink, but not in the ink zone which does not require ink. The size of the tiny gap in each ink zone not requiring ink is approximately equivalent to the size of a film gap that the ink duct roller forms together with the film roller. In each ink zone that does require ink, the enlargement of the tiny gap, corresponding to the respective ink demand, produces a metering gap. The thickness which is determined by the size of the metering gap, of an ink film fed out of the ink duct by the ink duct roller is so great that the film roller picks up some of this ink film.
Structurally and functionally advantageous refinements of the inking unit according to the invention are recited in the dependent claims and will become apparent from the ensuing description of an exemplary embodiment and the associated drawing.
Other features which are considered as characteristic for the invention are thus set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an inking unit in a printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: